CVE-2024-57256 in U-Boot
Summary
by MITRE • 02/19/2025
An integer overflow in ext4fs_read_symlink in Das U-Boot before 2025.01-rc1 occurs for zalloc (adding one to an le32 variable) via a crafted ext4 filesystem with an inode size of 0xffffffff, resulting in a malloc of zero and resultant memory overwrite.
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Analysis
by VulDB Data Team • 06/01/2025
The vulnerability identified as CVE-2024-57256 represents a critical integer overflow flaw within the ext4 filesystem handling code of Das U-Boot, a widely used open-source bootloader firmware. This issue specifically manifests in the ext4fs_read_symlink function, which processes symbolic links within ext4 filesystems. The vulnerability becomes exploitable when a maliciously crafted ext4 filesystem contains an inode with a size value of 0xffffffff, effectively representing the maximum value for a 32-bit unsigned integer. The flaw stems from improper handling of the zalloc operation where the code attempts to add one to a little-endian 32-bit variable without adequate overflow checking mechanisms.
The technical implementation of this vulnerability involves a classic integer overflow condition where the addition of one to the le32 variable results in an overflow that subsequently leads to a malloc call with a zero-sized parameter. This zero-sized memory allocation creates a dangerous scenario where the bootloader's memory management system allocates no memory but still proceeds with operations that expect valid memory allocation. The resulting memory overwrite occurs because the system attempts to write data to a memory location that either contains no allocated space or contains corrupted memory regions. This type of flaw falls under the CWE-190 category of Integer Overflow or Wraparound, which is particularly dangerous in embedded systems where memory corruption can lead to arbitrary code execution.
The operational impact of this vulnerability is severe for systems that rely on Das U-Boot for their boot process and firmware initialization. Attackers who can control or influence the filesystem content loaded during the boot process can potentially exploit this vulnerability to gain unauthorized control over the target device. The memory overwrite condition creates opportunities for attackers to manipulate critical bootloader structures, potentially leading to complete system compromise. This vulnerability is particularly concerning in embedded systems, IoT devices, and network infrastructure equipment where U-Boot serves as the primary boot loader and where attackers may have the ability to inject malicious filesystem content.
The exploitation of this vulnerability aligns with several ATT&CK techniques including T1059.001 for command and scripting interpreter and T1547.001 for registry run keys. The integer overflow in the filesystem parsing code creates a memory corruption condition that can be leveraged to execute arbitrary code within the bootloader environment. Systems affected by this vulnerability include any device running Das U-Boot versions prior to 2025.01-rc1 where ext4 filesystem support is enabled and where the system may be exposed to untrusted filesystem content. The vulnerability is particularly relevant in environments where devices may be connected to untrusted networks or where filesystem images can be modified by attackers. Organizations should prioritize upgrading to the patched version of Das U-Boot to prevent exploitation, while also implementing filesystem validation mechanisms to prevent loading of maliciously crafted ext4 images.
The root cause of this vulnerability demonstrates poor input validation and inadequate integer overflow protection in the bootloader's filesystem handling code. The lack of proper bounds checking when processing inode size values from external filesystem structures creates a direct path for attackers to manipulate memory allocation behavior. This type of vulnerability is commonly found in embedded systems where memory constraints and performance considerations may lead to insufficient security controls. The fix for this vulnerability requires implementing proper integer overflow detection and handling for the zalloc operation, ensuring that the addition operation does not result in an overflow condition that leads to zero-sized memory allocation. Additionally, the code should validate inode size parameters against reasonable limits to prevent malicious values from being processed.